1. Field of the Invention
The present invention relates to a light emitting device and a camera-equipped cellular phone incorporating the same and, more particularly, relates to a light emitting device employing light emitting elements such as light emitting diodes and a camera-equipped cellular phone incorporating the same as a secondary light source for use in photographing.
2. Description of Related Art
As a conventional technique relating to the present invention, there have been known light emitting devices which are mounted as secondary light sources in camera-equipped cellular phones and are structured to include a white LED and a blue LED mounted on a common substrate and include a common frame member covering the both LEDs for emitting white light and blue light, such that the white light is used as a secondary light source for use in photographing while the blue light is used as an incoming lamp (see for example, Japanese Unexamined Patent Publication No. 2006-295082).
Further, as another conventional technique relating to the present invention, there have been known light emitting devices structured to include a combination of a blue LED, a red LED and a green fluorescent material which is excited by blue light to emit green light, so that white light with an excellent color rendering characteristic is emitted with the two color chips (see for example, Japanese Unexamined Patent Publication No. 2004-327492).
In recent years, widespread use of camera-equipped cellular phones has been significantly advanced. Many of camera-equipped cellular phones incorporate a white-light emitting device employing light emitting diodes (LEDs) as a secondary light source to cope with photographing in dark places.
There are three main types of white-light emitting devices employing LEDs, as follows.
White-light emitting devices of the first type employ a combination of a blue LED and a YAG (yttrium aluminum garnet) based fluorescent material to cause color mixture of blue light and yellow light generated from the excited fluorescent material for emitting pseudo white light. However, such a pseudo white color has a poor color rendering characteristic due to the shortage of red components, which may induce a so-called “color seepage” phenomenon which biases the color shades of images created by photographing toward blue green colors in cases where the light emitting devices are used as secondary light sources.
White-light emitting devices of the second type employ a combination of LEDs for three colors of RGB to cause color mixture of the three colors of RGB for emitting white light.
White-light emitting devices of the third type employ a combination of a blue LED, a red LED and a green fluorescent material which is excited by blue light to emit green light, for causing color mixture of three colors of RGB with the two color chips for emitting white light.
Among white-light emitting devices of the aforementioned three types, those of the third type are capable of emitting white light with an excellent color rendering characteristic resulted from color mixture of three colors of RGB with a simple structure using LED chips for two colors and a fluorescent material. Therefore, it can be said that such white-light emitting devices of the third type are excellent in terms of mounting area and cost.
On the other hand, the recent widespread use of camera-equipped cellular phones has offered the function of photographing to cellular phones which are always carried, which have offered, to users, opportunities to photograph readily at various situations, regardless of time and place.
However, unfortunately, some users have conducted immoral acts such as secret photographing, by wrongly utilizing the advantage of readily photographing.
In order to prevent secret photographing and other acts, it is most important to improve the morals of users, but there is also a need for development of cellular phones capable of increasing the difficulty of secret photographing and the like.
In order to increase the difficulty of secret photographing, it is common practice to provide cellular phones structured to generate pseudo shutter sounds when their electronic shutters are pressed.
It is estimated that such pseudo shutter sounds have offered a certain effect of preventing secret photographing and the like, but such shutter sounds are cancelled in crowds in many cases. Therefore, there has been a need for further improvement in other respects than shutter sounds.